A typical V-type internal combustion engine has left and right cylinder banks arranged so as to define a V-shaped space therebetween. A row of cylinders in one of the cylinder banks is generally offset in a forward direction with respect to the vehicle in which it is mounted relative to a row of cylinders in the other cylinder bank. A cooling apparatus provided in such a V-type internal combustion engine typically has a water pump located at a central portion of the front end surface of a cylinder block and a cooling water passageway for introducing cooling water into the water pump. The passageway is typically formed in what is termed a "dead space" of the other cylinder between the front end of the engine and the foremost cylinder. An upstream part of the passageway usually extends to the side of the other cylinder block remote from the V-shaped space, and a downstream part thereof extends to the front end of the other cylinder block. The cooling water passageway is connected, at its upstream end, to a thermostat installed in the cooling system and, at its downstream end, to a pump chamber of the water pump. Such an arrangement, i.e., one having a cooling water passageway formed in the dead space with a row of cylinders in one cylinder bank offset forward with respect to the vehicle relative to a row of cylinders in the other cylinder bank, is known from, for instance, Japanese Utility Model Application No. 59-41105, entitled "Cooling Apparatus For V-Type Engine," filed on Mar. 22, 1984, and laid open as Japanese Unexamined Utility Model Publication No. 60-153818 on Oct. 14, 1985.
The passageway formed in the dead space of a cylinder bank as described in the above publication necessarily has a sharply curved downstream part opening to the front end of the cylinder bank. This sharply curved passageway part is apt to cause an increase in friction drag on the cooling water. Typically, in the case of engines designed to have rows of cylinders offset by a distance which is as short as possible for compactness, the passageway formed in the dead space, which is generally small in volume, is curved more sharply at its downstream part. Therefore, a great increase in friction drag on the cooling water is generated. This results in an insufficient cooling water supply to the water pump during a high speed operation of the engine.